I have recently brought an xr3i, I am finding it difficult to change gears especially when it is warm and there is a slight whirring noise when my foot is on the clutch? Is this my gearbox or clutch and is it a big job
cheers

 

It sounds like the clutch is dragging, don't worry about the whirring noise if only whilst pedal is pressed.
It may be a clutch that is getting a bit worn, but make sure that the pedal is going down 100% of the way, I have a similar problem because of my short legs, so seriously considering making a block for my clutch pedal!!
It can also be made worse with old crappy worn gearbox oil allowing the components to spin too easy so a change of oil in here would no doubt help as well.
tabetha